JP2002039299A - Auto-tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an inclination of a rotating member and to improve durability of an auto-tensioner. SOLUTION: An oscillating shaft 40 is fixed to a base 30 and a cup 52 of the rotating member 50 is rotatably fixed around the oscillating shaft 40. A cylindrical first sliding bearing 80 is provided between the oscillating shaft 40 and a bearing part 58 of the rotating member 50. A cylindrical damping band 92 used as a second sliding bearing is attached to the base 30 and a cup opening part 52 is supported from inside throughout its entire circumference. An arced supporting member 100 is concentrically provided in an outer side of the cup opening part 52, a third sliding bearing 110 is fixed to an inner side of the supporting member 100, and a part of the cup opening part 56 is supported from outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auto-tensioner for damping vibration while applying an appropriate tension to a drive belt.

[0002]

2. Description of the Related Art Generally, an auto-tensioner includes a swing shaft fixed to a base, a swing member swingably mounted around the swing shaft, and a swing shaft attached to one end of the swing member. A pulley having a parallel rotating shaft, a torsion coil spring for urging the pulley via a rotating member in a direction in which the belt is tensioned, and a damping mechanism for imparting resistance to the swing of the rotating member; When the moving member swings and the relative position of the pulley changes, appropriate tension is applied to the belt, and vibration generated in the belt is damped by damping the rotating member by the damping mechanism.

[0003]

In such an auto-tensioner, since the pulley is attached to the tip of the rotating member, the rotating member is not uniform around the swing axis due to the pressing force of the belt against the pulley. There is a problem that a load is applied and the rotating member is easily inclined. A sliding bearing made of synthetic resin is provided between the swinging shaft made of metal and the rotating member, but when the rotating member is tilted, the sliding bearing is relatively soft, causing uneven wear and early damage. When the rotating member rattles, abnormal noise is generated, and the torsion coil spring attached to the rotating member and the base repeatedly acts as a load, thereby causing cracks in the mounting portion. Although it has been considered to prevent premature wear by forming the sliding bearing from a material having excellent wear resistance, this alone is not sufficient.

SUMMARY OF THE INVENTION [0004] In view of the above problems, an object of the present invention is to prevent the rotation member from tilting and improve the durability of the auto tensioner.

[0005]

An auto-tensioner according to the present invention comprises a flat base for fixing a swing shaft, a cup opening toward the base, and a swing extending from the bottom of the cup to a middle position. A rotating member having a bearing portion supported by the drive shaft and rotatably supported around the swing shaft; a first cylindrical sliding bearing interposed between the swing shaft and the bearing portion; A cylindrical second sliding bearing fixed to the base, frictionally sliding on the inner peripheral surface near the opening of the cup portion to generate a damping force, and supporting the inner peripheral surface of the cup portion; and an outer peripheral surface of the cup portion. And a third sliding bearing having an arc shape for supporting the first, second, and third sliding bearings, wherein the first, second, and third sliding bearings are obtained by injection molding a thermoplastic resin having good heat resistance. First
In addition to the sliding bearing, the second and third sliding bearings support the rotating member, so that the overload of the first sliding bearing is reduced and the rotating member is hardly tilted. Generation of abnormal noise or cracking due to rattling of the moving member is prevented. Further, since the first, second and third sliding bearings are obtained by injection molding a thermoplastic resin having good heat resistance, the productivity is good.

The thermoplastic resin used as the material of the first to third sliding bearings may be a partially aromatic polyamide resin or a polyamideimide resin composition. These resins have characteristics such as a high melting point, that is, excellent heat resistance, good mechanical strength in a high-temperature environment, and excellent wear resistance and durability, and are suitable for sliding bearings.

The third sliding bearing may be formed integrally with the base and fixed to an arc-shaped support member along the outer peripheral surface of the cup portion, and may slide on the outer peripheral surface of the cup portion.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram schematically showing a belt system using an auto tensioner 20 of the first embodiment. The single endless belt 10 is hung around a driving pulley 12, a plurality of driven pulleys 14, and an idler 16, and rotates in synchronization with the driving pulley 12 to rotate each driven pulley 14. The pulley 70 of the auto tensioner 20 is
Abuts from the outside and rotates synchronously with the belt 10,
It relatively moves around a swing axis 40 parallel to the rotation axis 72 within a predetermined angle range, that is, between a first position indicated by a solid line and a second position indicated by a broken line in the figure.

More specifically, a rotatable rotating member 50 is attached to the swing shaft 40, and a pulley 70 is attached to the tip thereof. The rotating member 50 is a torsion coil spring (reference numeral 9).
0; FIG. 2), the belt 10 is urged in the direction of tension (rightward in the figure). When the belt 10 is vibrated, the rotating member 50 swings and the pulley 70 changes its relative position, whereby the belt 10 is always in contact with the pulley 70 and a constant tension is applied regardless of the vibration. At this time,
A damping mechanism (reference numerals 92 and 9)
6; FIG. 2), resistance is imparted, excessive swinging of the rotating member 50 is prevented, and vibration generated in the belt 10 is attenuated.

FIG. 2 is a view showing a cross section of the auto-tensioner 20, FIG. 3 is a plan view of the rotating member 50 side (from above in FIG. 2), and FIG. 4 is a base 30 side (from below in FIG. 2). It is the top view seen from.

The auto-tensioner 20 has a flat base 30 fixed to an engine block (not shown). A cylindrical shaft hole 32 protrudes vertically at substantially the center of one surface 30a of the base 30. One end of the swing shaft 40 is press-fitted and fixed inside the shaft hole 32.

The rotating member 50 has a cup 52 which opens to the base 30 side.
4, a cylindrical bearing portion 58 extending vertically toward the middle of the cup opening portion 56 and having openings at both ends thereof is provided integrally. A swing shaft 40 fixed to the base 30 is inserted into the bearing portion 58, and the rotating member 50 is rotatable about the swing shaft 40 as an axis. The movement of the cup 52 in the axial direction is restricted by the head 44 of the swing shaft 40 provided on the cup bottom surface 54 side.

A first sliding bearing 80 is press-fitted substantially inside the bearing portion 58 over substantially the entire axial direction.
0 rotates about the pivot shaft 40, the first sliding bearing 80
Slides frictionally with the swing shaft 40. The first sliding bearing 80 has a flange 82 at an end on the cup bottom 54 side, and the flange 82 is interposed between the cup bottom 54 and the head 44 of the swing shaft 40 to prevent wear due to interference between the two. Prevents early damage.

An arm 62 extending radially outward is integrally provided on the outer peripheral surface near the cup bottom portion 54, and a pulley 70 is attached to a tip of the arm 62 by a rotary shaft 72 which is a bolt. The pulley 70 is disposed on the side of the base 30 (the lower side in the figure) with respect to the arm 62, and the rotation shaft 72 is
Is rotatable around the axis C1.

The swing shaft 40 is formed with a cylindrical bolt hole 46 which is open at both ends. After the auto tensioner 20 is assembled in the state shown in FIG. The automatic tensioner 2 is inserted into the engine block and screwed and fixed at a predetermined position on the engine block.
0 is attached to the engine block. As shown in FIG. 3, the base 30 is provided with two mounting portions 36 extending radially outward from a portion facing the cup 52, and bolts (not shown) are provided in the bolt holes 3 of the mounting portions 36.
8 are respectively screwed and fixed to the engine block. That is, the base 30 is fixed not only to the swing shaft 40 located at the rotation axis C2 of the rotation member 50 but also to two bolt holes 38 deviated from the rotation axis C2. Relative rotation is prevented.

A torsion coil spring 90 spirally wound around the swing shaft 40 is accommodated in the cup 52 in a state of being appropriately compressed.
0 and the cup bottom 54. Accordingly, the rotating member 50 is urged in the direction in which the torsion coil spring 90 extends around the swing shaft 40, and the belt 10 is pressed in the direction in which the belt 10 is tightened by the pulley 70 relatively moving with the rotating member 50.

In the cup opening 56, a damping band 92 as a second sliding bearing, and the damping band 92
And a ring spring 96 for biasing the spring. The damping band 92 is an annular member that slides over substantially the entire inner peripheral surface 56 a of the cup opening 56. The damping band 92 is on one side 3 of the base 30.
0a for engaging the pin 34 protruding from the
The damping band 92 is fixed to the base 30 by the engagement of the pin 34 and the pin hole 94. The damping band 92 exerts a uniform force in the circumferential direction toward the outside in the radial direction, that is, toward the inner peripheral surface 56 a of the cup opening 56, by the spring force of the two ring springs 96 axially overlapped on the inside. To provide resistance when the cup opening 56 rotates relative to the base 30, that is, when the rotating member 50 swings. Thus, the pulley 70 is braked together with the rotating member 50, and the vibration of the belt 10 is attenuated.

The damping band 92 is connected to the cup opening 5.
6 also has a function as a sliding bearing that supports the inner peripheral surface 56a in the radial direction. The damping band 92 is the base 30
Is fixed directly at a position very close to the mounting portion 36, so that the relative movement amount is extremely small and stable, and furthermore, the ring spring 96 is urged radially outward with a uniform force in the circumferential direction, so that it is radially Less stress deformation. Further, since the diameter of the damping band 92 is larger than the diameter of the first sliding bearing 80, a large supporting area can be secured, and a large supporting force in the radial direction can be obtained.

Therefore, the cup opening 56, that is, the rotating member 5
The support strength of 0, particularly the support strength in the radial direction is remarkably improved, and the rotating member 50 is hardly inclined. Further, the load on the first slide bearing 80 is reduced, and the durability of the first slide bearing 80 is improved.

A support member 100 having an arc-shaped cross section is provided outside the outer peripheral surface 56b of the cup opening 56. The support member 100 is formed integrally with the base 30 by an aluminum alloy, and swings vertically from one surface 30a of the base 30. Active axis C
Extends along 2. The support member 100 has a cup opening 56.
Wall 102 having an arcuate cross-section formed concentrically outside
And first and second locking walls 104, 1 and 1 extending radially inward from two side edges of the support wall 102, respectively.
06. Support wall 102, first and second locking walls 1
The third slide bearing 110 is inserted into the space formed by the first and second slide bearings 04 and 106 and the cup opening 56 with substantially no gap.

As shown in FIG. 3, the cup 52 includes first and second projections 53 and 55 projecting radially outward from the outer peripheral surface. The first projection 53 is provided on the first locking wall 104 and the second projection. 5
Reference numerals 5 face the second locking walls 106, respectively. The support member 100 and the third slide bearing 110 are provided over a range of an angle θ1 about the rotation axis C2. The angle θ1 is approximately 90 degrees in FIG. 3, but may be within a range of about 90 degrees to 180 degrees, and can be changed as appropriate.

The angle θ2 between the first and second protrusions 53 and 55 on the side where the support member 100 is sandwiched is larger than the angle θ1.
The rotation of the rotating member 50 is allowed only within the angle range of the difference (θ2−θ1). First and second locking walls 10
Reference numerals 4 and 106 function as rotation stoppers for preventing the rotation of the rotation member 50 by (θ2−θ1) or more, and the first protrusions 53 at the first position where the belt 10 is most tensioned as shown by the solid line in FIG. Abuts on the first locking wall 104, and the second protrusion 55 abuts on the second locking wall 106 at the second position where the belt 10 is most relaxed as shown by the broken line in FIG. 1. Note that the angle θ2 is set to a value that is approximately 30 to 60 degrees larger than the angle θ1.

The third sliding bearing 110 includes a curved plate portion 112 curved along both the inner peripheral surface of the support member 100 and the outer peripheral surface 56b of the cup opening 56, and the curved plate portion 11
And an engagement piece 114 extending radially outward from an end of the second cup opening 56 side.

The curved plate portion 112 is sandwiched between the two locking walls 104 of the support member 100 while being bent in the circumferential direction.
Thereby, the relative movement of the third slide bearing 110 in the circumferential direction with respect to the base 30 is restricted. The engagement piece 114 engages with an engagement hole 108 formed at a corner between the support wall 102 and the base 30, thereby restricting the relative movement of the third slide bearing 110 with respect to the base 30 along the axial direction C <b> 2. Is done. Thus, the third slide bearing 110 is supported by the support member 10.
0, which is fixed to the base 30 and the cup opening 56
The outer peripheral surface 56b is radially supported from the outside, and the rotating member 50 frictionally slides with the outer peripheral surface 56b on the curved plate portion 112 when the rotating member 50 rotates around the pivot axis C2.

The materials of the first sliding bearing 80, the damping band 92 as the second sliding bearing, and the third sliding bearing 110 include heat resistance, mechanical strength at high temperature, friction coefficient, abrasion resistance, and productivity. It is preferable to use a synthetic resin which does not damage the sliding surface of the mating member, specifically, the rocking shaft 40 formed of steel or the rotating member 50 formed of an aluminum alloy. It is preferable that the resin is a thermoplastic resin that can be integrally molded. Specific examples of suitable thermoplastic resins together with their abbreviations include polyamide resin (PA) represented by nylon 66, polyether sulfone resin (PES), polyphenylene sulfide resin (PPS), and polyamide imide resin (PA).
I), a partially aromatic polyamide resin represented by nylon 6T and the like. These thermoplastic resins may be used alone, but two or more resins may be blended in order to obtain desired properties.

Depending on the purpose, the thermoplastic resin may include reinforcing materials such as glass fiber, carbon fiber and aramid fiber,
Fluorine compounds represented by polytetrafluoroethylene resin (PTFE), solid lubricants such as molybdenum disulfide and graphite, or flame retardants, plasticizers, release agents, weathering agents,
Various additives such as an antistatic agent and a colorant are added alone or in combination of two or more.

First to third sliding bearings 80, 92 and 11
0 is integrally manufactured by injection molding. Therefore, since special machining such as cutting is not required, the cost is low and the productivity is high. The first to third slide bearings 80, 92 and 110 may all be formed from the same composition,
It is preferable to form the composition from different compositions according to the respective properties.

The rotating member 50 is formed of a soft metal aluminum alloy, but the frictional sliding damping band 9 is used.
Since the second and third sliding bearings 110 are formed of a synthetic resin having low aggressiveness with respect to the counterpart material, the rotating member 50 is less worn and the cup opening 56 can always be directly supported without any gap.

FIG. 5 is a partial perspective view showing the vicinity of the support member 100 and the third slide bearing 110 by partially breaking it, and FIG. 6 is a partially enlarged plan view thereof.

The engagement hole 108 is provided between the support member 100 and the base 3.
0 is cut from the outer peripheral side over a predetermined circumferential length, the radial width W1 is larger than the thickness W2 of the support wall 102, and the gap is large enough to allow the locking piece 114 to be inserted from the inside. Are formed. The radial length W of the gap
3 is set to a value smaller than the thickness W4 of the curved plate portion 112 of the third sliding bearing 110 so that the third sliding bearing 110 does not fall off.

The circumferential length of the third sliding bearing 110 is a natural length slightly longer than the distance between the first and second locking walls 104 and 106. Is inserted between the first and second locking walls 104 and 106 while being bent in the circumferential direction. Curved plate 112
And second locking walls 104, 106 abutting the side surfaces of the
Is smaller than the thickness W4 of the curved plate portion 112, and the curved surfaces 104a and 106a are located on the outer peripheral side of the inner peripheral surface 112a of the curved plate portion 112. Accordingly, only the curved plate portion 112 is in close contact with the outer peripheral surface 56b of the cup opening 56, and the buffer between the first and second locking walls 104 and 106 and the cup opening 56 is avoided.

The rotating member 50 is mounted with the third slide bearing 110 and the damping band 92 mounted on the base 30 in advance, so that the cup opening 56 is formed in the third opening.
In order to facilitate insertion between the sliding bearing 110 and the damping band 92, a corner 112b of the curved plate 112 on the cup opening 56 side is rounded.

Next, referring to FIG. 7 and FIG.
00 and the arrangement of the third slide bearing 110 will be described.
FIG. 7 is a sectional view conceptually showing a load applied to the rotating member by the pressing force from the belt 10, and FIG. 8 is a plan view thereof.

First, a plane parallel to the axes C1 and C2 (FIG. 7) will be described. When the pulley 70 is pressed from the belt 10 in the direction of arrow P, the line of action CL1 is moved to the bearing supported by the swing shaft 40. Since the rotating member 50 is located closer to the base 30 than the portion 58, the rotating member 50 has a force tilting toward the pulley 70, specifically, a moment Ma for rotating the bearing portion 58 clockwise about the load center M of the bearing portion 58. Works.

The counterclockwise moment Mb balanced with the moment Ma is applied to the bearing 58 and the first sliding bearing 8.
It is generated by the urging force F2 that combines the drag F1 of the swing shaft 40 at zero, the drag of the fixed damping band 92, and the spring force of the ring spring 96. Note that FIG. 7 shows only one or two F1 and F2 as representatives, but actually occur over the entire axial direction.

The moment M is caused by the vibration of the belt 10 or the like.
When a becomes larger than Mb, the cup 56 rotates about the bearing load center M, and the cup opening 56 farthest from the bearing 58 is displaced the most. In particular, in FIG. 7, a portion X (indicated by hatching) of the cup opening 56, particularly a portion X far from the pulley 70, is easily displaced so as to float with respect to the base 30.

Therefore, the support member 100 for supporting the portion X from outside the cup opening 56 and the third sliding bearing 11
0, and the support member 100
And the third sliding bearing 110 is pressed, and the reaction causes the cup opening 56 to move toward the axis C2 (arrow F3 in the figure).
). The drag F3 contributes to the moment Mb for rotating the rotating member 50 in the counterclockwise direction, so that the load on the swing shaft 40, the bearing 58, and the first sliding bearing 80 is reduced, and the softest sliding is achieved. Uneven wear and early crack damage of the bearing 80 can be prevented, and rattling is less likely to occur.

The magnitude of the moment generated by the drag F3 is determined by the axial distance r from the bearing load center M of the bearing portion 58 and the pressing force F of the support member 100 and the third sliding bearing 110.
3, the inclination of the rotating member 50 can be effectively prevented by providing the support member 100 and the third sliding bearing 110 in the cup opening 56 where the distance r is the largest, with a smaller drag F3. The same applies to the urging force F2. Since the damping band 92 and the ring spring 96 are arranged in the cup opening 56,
The moment around the bearing load center M can be increased.

The plane perpendicular to the axes C1 and C2 in FIG. 8 will be described. When the pulley 70 is pressed by the belt 10, the load P is applied to the rotating shaft 72 along the action line indicated by the one-dot chain line CL1. I do. The moment Ma is applied to the swing shaft 40 supporting the rotating member 50 integral with the rotating shaft 72 in a direction parallel to the line of action (indicated by a dashed line CL2 in the figure).
(FIG. 7) operates.

Accordingly, the portion X having the largest displacement is located on the line of action CL2 in the circumferential direction and the belt 10
Located far from The support member 100 and the third sliding bearing 110 are arranged so that their centers in the circumferential direction coincide with the action line CL2, and support the portion X. This allows
The portion X having the largest displacement can be reliably supported, and the rotating member 5
The inclination of 0 can be effectively suppressed. This inclination suppressing action is exhibited when the rotating member 50 is inclined by a small amount.

The thickness of the support member 100 and the third slide bearing 110, that is, the strength is determined by the load P received from the belt 10 and the distance r.
And the distance between the bearing load center M and the action line CL1 is appropriately changed. Further, the relative positions of the support member 100 and the third sliding bearing 110 in the circumferential direction are appropriately changed according to the axial position of the pulley 70 with respect to the bearing load center CL2 and the position where the belt 10 is bridged.

Referring to FIGS. 9 and 10, an auto tensioner 120 according to the second embodiment will be described. FIG. 9 is a sectional view, and FIG. 10 is a plan view. The second embodiment has the same configuration as the first embodiment except that the axial position of the pulley 70 with respect to the bearing load center CL2 and the circumferential positions of the support member and the third slide bearing are different. The same components as those of the embodiment are denoted by the same reference numerals, and description thereof is omitted. Corresponding components are indicated by adding 100 to the reference numerals.

At the end of an arm 162 extending radially outward from the outer peripheral surface of the cup 52, a pulley 70
Mounted from the other side. As shown in FIG. 9, the center of the load received from the pulley 70 in the axial direction (the position indicated by the line of action CL <b> 1) is located on the opposite side of the base 30 with respect to the bearing 58, so that the rotating member 50 A moment Ma 'acting to rotate in a counterclockwise direction about the load center M of the portion 58, that is, in a direction opposite to the moment Ma of the first embodiment acts. Accordingly, the portion X of the rotating member 50 where the displacement is greatest is on the line of action CL2 in the circumferential direction and close to the belt 10.

Therefore, in the second embodiment, the support member 200 and the third slide bearing 210 are on the side near the pulley (lower right in FIG. 10), and the center in the circumferential direction is the action line C.
It is arranged so as to coincide with L2 and supports the site X.
In FIG. 10, the reaction force of the swing shaft 40 and the first slide bearing 80 is indicated by F1 ′, the biasing force by the damping band 92 and the ring spring 96 is indicated by F2 ′, and the reaction force of the support member 200 and the third slide bearing 210 is indicated by F3 ′. . As described above, also in the second embodiment, even when the rotating member 50 starts to tilt, the portion X where displacement is largest can be reliably supported, and the tilting of the rotating member 50 can be effectively prevented.

As described above, in the auto tensioner 20 (120) of the first (second) embodiment, not only the first sliding bearing 80 but also the damping band 92 and the third sliding bearing 110 (210) are pivotable members. Since the rotating member 50 is supported in the radial direction, inclination of the rotating member 50 is prevented, and uneven wear and early damage of the first sliding bearing 80 and the head 44 of the swing shaft 40 are prevented.
Generation of abnormal noise due to rattling can be prevented, and the durability of the auto tensioner 20 (120) can be improved.
The damping band 92 as the second plain bearing is formed on the base 3
0, and has a diameter larger than that of the first sliding bearing 80, so that the radial supporting force on the rotating member 50 is increased, and the load on the first sliding bearing 80 is reduced. Since the third sliding bearing 110 (210) directly supports the portion X that is most displaced when the moment Ma (Ma ') acts on the rotating member 50, the third sliding bearing 110 (210) is particularly inclined when the rotating member 50 is slightly inclined. Exhibits a deterrent effect.

In this embodiment, the third sliding bearing 110 (210) is fixed to the support member 100 (200) and slides frictionally with the cup opening 56. It may be fixed to the outer peripheral surface of the opening 56 and frictionally slid with the support member 100.

[0048]

According to the present invention, the inclination of the rotating member is prevented, and the durability of the auto tensioner is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a belt system using an auto tensioner according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the auto tensioner shown in FIG.

FIG. 3 is a top view of the auto tensioner shown in FIG.

FIG. 4 is a bottom view of the auto tensioner shown in FIG.

FIG. 5 is a partial sectional perspective view of a support member and a third slide bearing.

FIG. 6 is a plan view of a support member and a third slide bearing as viewed from a base constant surface side.

FIG. 7 is a sectional view conceptually showing a load applied to a rotating member.

FIG. 8 is a plan view conceptually showing a load applied to a rotating member.

FIG. 9 is a sectional view of an auto-tensioner according to a second embodiment of the present invention.

FIG. 10 is a bottom view of the auto tensioner shown in FIG. 9;

[Explanation of symbols]

 Reference Signs List 20 auto tensioner 30 base 40 swing shaft 50 rotating member 52 cup 70 pulley 80 first sliding bearing 92 damping band (second sliding bearing) 100 support member 110 third sliding bearing

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F16H 7/08 F16H 7/08 Z // B29K 77:00 B29K 77:00 79:00 79:00 B29L 31:04 B29L 31:04

Claims (3)

[Claims] 1. A base for fixing an oscillating shaft, a cup portion opening toward the base, and a bearing portion extending from a bottom surface of the cup portion to a middle and supported by the oscillating shaft. A rotating member rotatably supported around the swing shaft; and a first cylindrical member interposed between the swing shaft and the bearing portion.
A sliding second bearing that is fixed to the base and frictionally slides on an inner peripheral surface near an opening of the cup portion to generate a damping force and supports the inner peripheral surface of the cup portion; An arc-shaped third sliding bearing that supports an outer peripheral surface of the cup portion, wherein the first, second, and third sliding bearings are obtained by injection molding a thermoplastic resin having good heat resistance. An auto tensioner characterized by the following. 2. The auto tensioner according to claim 1, wherein the thermoplastic resin is a composition of a partially aromatic polyamide resin or a polyamideimide resin. 3. The third sliding bearing is fixed to an arc-shaped support member formed integrally with the base and curved along the outer peripheral surface of the cup portion, and frictionally slides on the outer peripheral surface of the cup portion. The auto-tensioner according to claim 1, wherein: